FIELD OF THE INVENTION AND RELATED ART STATEMENT
The present invention generally relates to an endoscope system in which a plurality of light source apparatuses, which can be used by switching, are synchronized with a common video signal processing apparatus by a synchronizing signal to obtain a plurality of different picture images.
Recently, an endoscope has been widely used whereby, by inserting an elongated insertable part of the endoscope into the body cavity, internal organs in the body cavity can be observed and several kinds of medical treatments can be applied by using the treatment tools inserted into treatment channels as the occasion demands. Also, various electronic endoscopes in which a solid state imaging device, such as a CCD, is used in an imaging system have been proposed.
It has been recognized that knowing the distribution of the quantity of hemoglobin and the distribution of the degree of saturation with oxygen in blood is helpful in early discovery of a pathological change. It has also been recognized that the observation of the images not only in a visible light range but also in an infrared rays range allows to observe a pathological change which is difficult to be observed in an ordinary visible light range.
For example, as shown in the Gazette of Japanese Patent Laid Open No. 217415/1989, an apparatus having a plurality of filers (including at least a filter which can sequentially separate a light emitted from a light source into three wavelength ranges where a color picture can be formed) are insertably arranged in the light source and on the illuminating optical path and filter switching means where one of the above mentioned plurality of filters can be selectively inserted on the illuminating optical path is disclosed so that a plurality of lights including a frame sequential light which can form a color picture image can be supplied by switching the filters with the filter switching means.
Also, as shown in the Gazette of Japanese Patent Laid Open No. 76827/1989, in an electronic endoscope apparatus displaying a video signal of a subject image, such as an affected part taken by an imaging device of CCD or the like on a monitor TV fitted outside, a device which is operated is disclosed as having first irradiating means for irradiating a subject with near infrared rays, second irradiating means for irradiating a subject with visible rays through a light guide and selecting control means for selecting either case of the first or second irradiating means.
However, the structure of the above mentioned Japanese Patent Laid Open No. 217415/1989 has a problem. That is, since a driving part for selecting a plurality of rotary filters is provided and is used for a special examination which is not needed for an ordinary observation, the light source body becomes larger, at the same time, an effective exclusive light source cannot be used.
Also, the device shown in Japanese Patent Laid Open No. 76827/1989 has a problem whereby the device cannot be used for a system requiring a shading period of an illuminating light and cannot process a characteristic requiring attention by making the characteristic remarkable by a picture image calculation among different wavelengths because only one wavelength, such as a laser beam, is used.